Introduction

Apache Tribes supports an interceptor architecture to intercept both messages and membership notifications.
This architecture allows decoupling of logic and opens the way for some very kewl feature add ons.

Static Membership

In addition to dynamic discovery, Apache Tribes also supports static membership, with membership verification.
To achieve this add the org.apache.catalina.tribes.group.interceptors.StaticMembershipInterceptor
underneath the org.apache.catalina.tribes.group.interceptors.TcpFailureDetector interceptor.
Inside the StaticMembershipInterceptor you can add the static members you wish to have.
The TcpFailureDetector will do a health check on the static members,and also monitor them for crashes
so they will have the same level of notification mechanism as the members that are automatically discovered.

Attributes

Common Attributes

Attribute

Description

className

Required, as there is no default

optionFlag

If you want the interceptor to trigger on certain message depending on the message's option flag,
you can setup the interceptors flag here.
The default value is 0, meaning this interceptor will trigger on all messages.

The logical cluster domain that this Interceptor accepts.
Two different type of values are possible:
1. Regular string values like "staging-domain" or "tomcat-cluster" will be converted into bytes
using ISO-8859-1 encoding.
2. byte array in string form, for example {216,123,12,3}

logInterval

This value indicates the interval for logging for messages from different domains.
The default is 100, which means that to log per 100 messages.

The default and hard coded value is 8 (org.apache.catalina.tribes.Channel.SEND_OPTIONS_ASYNCHRONOUS).
The dispatcher will trigger on this value only, as it is predefined by Tribes.

alwaysSend

What behavior should be executed when the dispatch queue is full. If true (default), then the message is
is sent synchronously, if false an error is thrown.

maxQueueSize

Size in bytes of the dispatch queue, the default value is 1024*1024*64 (64MB) sets the maximum queue size for the dispatch queue
if the queue fills up, one can trigger the behavior, if alwaysSend is set to true, the message will be sent synchronously
if the flag is false, an error is thrown

maxThreads

The maximum number of threads in this pool, default is 10.

maxSpareThreads

The number of threads to keep in the pool, default is 2.

keepAliveTime

Maximum number of milliseconds of until Idle thread terminates. Default value is 5000(5 seconds).

Specifies the timeout, in milliseconds, to use when attempting a TCP connection
to the suspect node. Default is 1000.

performSendTest

If true is set, send a test message to the suspect node. Default is true.

performReadTest

If true is set, read the response of the test message that sent. Default is false.
Note: if performSendTest is false, this attribute will have no effect.

readTestTimeout

Specifies the timeout, in milliseconds, to use when performing a read test
to the suspicious node. Default is 5000.

removeSuspectsTimeout

The maximum time(in seconds) for remove from removeSuspects. Member of
removeSuspects will be automatically removed after removeSuspectsTimeout.
If a negative value specified, the removeSuspects members never be
removed until disappeared really. If the attribute is not provided,
a default of 300 seconds (5 minutes) is used.

If useThread == true, defines the interval of sending a ping message.
default is 1000 ms.

useThread

Flag of whether to start a thread for sending a ping message.
If set to true, this interceptor will start a local thread for sending a ping message.
if set to false, channel heartbeat will send a ping message.
default is false.

Defines the interval in number of messages when we are to report the throughput statistics.
The report is logged to the org.apache.juli.logging.LogFactory.getLog(ThroughputInterceptor.class)
logger under the INFO level.
Default value is to report every 10000 messages.

Nested Components

StaticMember Attributes

LocalMember:
Static member that is the local member of the static cluster group.

Attribute

Description

className

Only one implementation available:org.apache.catalina.tribes.membership.StaticMember

port

There is no need to set.
The value of this attribute inherits from the cluster receiver setting.

securePort

There is no need to set.
The value of this attribute inherits from the cluster receiver setting.

host

There is no need to set.
The value of this attribute inherits from the cluster receiver setting.

domain

The logical cluster domain for that this static member listens for cluster messages.
Two different type of values are possible:
1. Regular string values like "staging-domain" or "tomcat-cluster" will be converted into bytes
using ISO-8859-1 encoding.
2. byte array in string form, for example {216,123,12,3}

uniqueId

A universally uniqueId for this static member.
The values must be 16 bytes in the following form:
1. byte array in string form, for example {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15}

Member:
Static member that add to the static cluster group.

Attribute

Description

className

Only one implementation available:org.apache.catalina.tribes.membership.StaticMember

port

The port that this static member listens to for cluster messages

securePort

The secure port this static member listens to for encrypted cluster messages
default value is -1, this value means the member is not listening on a secure port

host

The host (or network interface) that this static member listens for cluster messages.
Three different type of values are possible:
1. IP address in the form of "216.123.1.23"
2. Hostnames like "tomcat01.mydomain.com" or "tomcat01" as long as they resolve correctly
3. byte array in string form, for example {216,123,12,3}

domain

The logical cluster domain for that this static member listens for cluster messages.
Two different type of values are possible:
1. Regular string values like "staging-domain" or "tomcat-cluster" will be converted into bytes
using ISO-8859-1 encoding.
2. byte array in string form, for example {216,123,12,3}

uniqueId

A universally uniqueId for this static member.
The values must be 16 bytes in the following form:
1. byte array in string form, for example {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15}